In general, a phosphor wavelength conversion material has been used as a material converting light having a certain wavelength emitted by various light sources into light having a desired wavelength. In particular, among various light sources, light emitting diodes (LEDs) are able to be driven with low power consumption and have excellent light efficiency, and thus may be effectively applied to liquid crystal display (LCD) backlight units, vehicle lighting systems, and home lighting systems. Recently, phosphor materials have been recognized as a core technology of the manufacturing of white light emitting devices.
White light emitting devices have been generally manufactured in a scheme in which at least one or more types of phosphor, for example, a yellow or red phosphor and a blue phosphor, are applied to a blue or ultraviolet LED chip. Such phosphors are required to have excellent thermal stability with relatively high light emission characteristics.
Here, as a red phosphor, red phosphors such as a sulfide-based or oxide-based phosphors or a nitride-based phosphor may be mainly used. In such red phosphors, e.g., sulfide-based and oxide-based phosphors, a phenomenon in which color is changed when driven for a long period of time may occur due to these phosphors having relatively low thermal and structural stability. Such a phenomenon may be severe in the field of illumination using high output LEDs.